[xdp-hints] Re: [RFC bpf-next 03/23] ice: make RX checksum checking code more reusable

[Maciej Fijalkowski <maciej.fijalkowski@intel.com>]

On Thu, Aug 24, 2023 at 09:26:42PM +0200, Larysa Zaremba wrote:
> Previously, we only needed RX checksum flags in skb path,
> hence all related code was written with skb in mind.
> But with the addition of XDP hints via kfuncs to the ice driver,
> the same logic will be needed in .xmo_() callbacks.
> 
> Put generic process of determining checksum status into
> a separate function.
> 
> Now we cannot operate directly on skb, when deducing
> checksum status, therefore introduce an intermediate enum for checksum
> status. Fortunately, in ice, we have only 4 possibilities: checksum
> validated at level 0, validated at level 1, no checksum, checksum error.
> Use 3 bits for more convenient conversion.
> 
> Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
> ---
>  drivers/net/ethernet/intel/ice/ice_txrx_lib.c | 105 ++++++++++++------
>  1 file changed, 69 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
> index b2f241b73934..8b155a502b3b 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
> @@ -102,18 +102,41 @@ ice_rx_hash_to_skb(const struct ice_rx_ring *rx_ring,
>  		skb_set_hash(skb, hash, ice_ptype_to_htype(rx_ptype));
>  }
>  
> +enum ice_rx_csum_status {
> +	ICE_RX_CSUM_LVL_0	= 0,
> +	ICE_RX_CSUM_LVL_1	= BIT(0),
> +	ICE_RX_CSUM_NONE	= BIT(1),
> +	ICE_RX_CSUM_ERROR	= BIT(2),
> +	ICE_RX_CSUM_FAIL	= ICE_RX_CSUM_NONE | ICE_RX_CSUM_ERROR,
> +};
> +
>  /**
> - * ice_rx_csum - Indicate in skb if checksum is good
> - * @ring: the ring we care about
> - * @skb: skb currently being received and modified
> + * ice_rx_csum_lvl - Get checksum level from status
> + * @status: driver-specific checksum status
> + */
> +static u8 ice_rx_csum_lvl(enum ice_rx_csum_status status)
> +{
> +	return status & ICE_RX_CSUM_LVL_1;
> +}
> +
> +/**
> + * ice_rx_csum_ip_summed - Checksum status from driver-specific to generic
> + * @status: driver-specific checksum status
> + */
> +static u8 ice_rx_csum_ip_summed(enum ice_rx_csum_status status)
> +{
> +	return status & ICE_RX_CSUM_NONE ? CHECKSUM_NONE : CHECKSUM_UNNECESSARY;

	return !(status & ICE_RX_CSUM_NONE);

?

> +}
> +
> +/**
> + * ice_get_rx_csum_status - Deduce checksum status from descriptor
>   * @rx_desc: the receive descriptor
>   * @ptype: the packet type decoded by hardware
>   *
> - * skb->protocol must be set before this function is called
> + * Returns driver-specific checksum status
>   */
> -static void
> -ice_rx_csum(struct ice_rx_ring *ring, struct sk_buff *skb,
> -	    union ice_32b_rx_flex_desc *rx_desc, u16 ptype)
> +static enum ice_rx_csum_status
> +ice_get_rx_csum_status(const union ice_32b_rx_flex_desc *rx_desc, u16 ptype)
>  {
>  	struct ice_rx_ptype_decoded decoded;
>  	u16 rx_status0, rx_status1;
> @@ -124,20 +147,12 @@ ice_rx_csum(struct ice_rx_ring *ring, struct sk_buff *skb,
>  
>  	decoded = ice_decode_rx_desc_ptype(ptype);
>  
> -	/* Start with CHECKSUM_NONE and by default csum_level = 0 */
> -	skb->ip_summed = CHECKSUM_NONE;
> -	skb_checksum_none_assert(skb);
> -
> -	/* check if Rx checksum is enabled */
> -	if (!(ring->netdev->features & NETIF_F_RXCSUM))
> -		return;
> -
>  	/* check if HW has decoded the packet and checksum */
>  	if (!(rx_status0 & BIT(ICE_RX_FLEX_DESC_STATUS0_L3L4P_S)))
> -		return;
> +		return ICE_RX_CSUM_NONE;
>  
>  	if (!(decoded.known && decoded.outer_ip))
> -		return;
> +		return ICE_RX_CSUM_NONE;
>  
>  	ipv4 = (decoded.outer_ip == ICE_RX_PTYPE_OUTER_IP) &&
>  	       (decoded.outer_ip_ver == ICE_RX_PTYPE_OUTER_IPV4);
> @@ -146,43 +161,61 @@ ice_rx_csum(struct ice_rx_ring *ring, struct sk_buff *skb,
>  
>  	if (ipv4 && (rx_status0 & (BIT(ICE_RX_FLEX_DESC_STATUS0_XSUM_IPE_S) |
>  				   BIT(ICE_RX_FLEX_DESC_STATUS0_XSUM_EIPE_S))))
> -		goto checksum_fail;
> +		return ICE_RX_CSUM_FAIL;
>  
>  	if (ipv6 && (rx_status0 & (BIT(ICE_RX_FLEX_DESC_STATUS0_IPV6EXADD_S))))
> -		goto checksum_fail;
> +		return ICE_RX_CSUM_FAIL;
>  
>  	/* check for L4 errors and handle packets that were not able to be
>  	 * checksummed due to arrival speed
>  	 */
>  	if (rx_status0 & BIT(ICE_RX_FLEX_DESC_STATUS0_XSUM_L4E_S))
> -		goto checksum_fail;
> +		return ICE_RX_CSUM_FAIL;
>  
>  	/* check for outer UDP checksum error in tunneled packets */
>  	if ((rx_status1 & BIT(ICE_RX_FLEX_DESC_STATUS1_NAT_S)) &&
>  	    (rx_status0 & BIT(ICE_RX_FLEX_DESC_STATUS0_XSUM_EUDPE_S)))
> -		goto checksum_fail;
> -
> -	/* If there is an outer header present that might contain a checksum
> -	 * we need to bump the checksum level by 1 to reflect the fact that
> -	 * we are indicating we validated the inner checksum.
> -	 */
> -	if (decoded.tunnel_type >= ICE_RX_PTYPE_TUNNEL_IP_GRENAT)
> -		skb->csum_level = 1;
> +		return ICE_RX_CSUM_FAIL;
>  
>  	/* Only report checksum unnecessary for TCP, UDP, or SCTP */
>  	switch (decoded.inner_prot) {
>  	case ICE_RX_PTYPE_INNER_PROT_TCP:
>  	case ICE_RX_PTYPE_INNER_PROT_UDP:
>  	case ICE_RX_PTYPE_INNER_PROT_SCTP:
> -		skb->ip_summed = CHECKSUM_UNNECESSARY;
> -		break;
> -	default:
> -		break;
> +		/* If there is an outer header present that might contain
> +		 * a checksum we need to bump the checksum level by 1 to reflect
> +		 * the fact that we have validated the inner checksum.
> +		 */
> +		return decoded.tunnel_type >= ICE_RX_PTYPE_TUNNEL_IP_GRENAT ?
> +		       ICE_RX_CSUM_LVL_1 : ICE_RX_CSUM_LVL_0;
>  	}
> -	return;
>  
> -checksum_fail:
> -	ring->vsi->back->hw_csum_rx_error++;
> +	return ICE_RX_CSUM_NONE;
> +}
> +
> +/**
> + * ice_rx_csum_into_skb - Indicate in skb if checksum is good
> + * @ring: the ring we care about
> + * @skb: skb currently being received and modified
> + * @rx_desc: the receive descriptor
> + * @ptype: the packet type decoded by hardware
> + */
> +static void
> +ice_rx_csum_into_skb(struct ice_rx_ring *ring, struct sk_buff *skb,
> +		     const union ice_32b_rx_flex_desc *rx_desc, u16 ptype)
> +{
> +	enum ice_rx_csum_status csum_status;
> +
> +	/* check if Rx checksum is enabled */
> +	if (!(ring->netdev->features & NETIF_F_RXCSUM))
> +		return;
> +
> +	csum_status = ice_get_rx_csum_status(rx_desc, ptype);
> +	if (csum_status & ICE_RX_CSUM_ERROR)
> +		ring->vsi->back->hw_csum_rx_error++;
> +
> +	skb->ip_summed = ice_rx_csum_ip_summed(csum_status);
> +	skb->csum_level = ice_rx_csum_lvl(csum_status);
>  }
>  
>  /**
> @@ -229,7 +262,7 @@ ice_process_skb_fields(struct ice_rx_ring *rx_ring,
>  	/* modifies the skb - consumes the enet header */
>  	skb->protocol = eth_type_trans(skb, rx_ring->netdev);
>  
> -	ice_rx_csum(rx_ring, skb, rx_desc, ptype);
> +	ice_rx_csum_into_skb(rx_ring, skb, rx_desc, ptype);
>  
>  	if (rx_ring->ptp_rx)
>  		ice_ptp_rx_hwts_to_skb(rx_ring, rx_desc, skb);
> -- 
> 2.41.0
>